It was said to al-Hasan, 'People say that whoever says, 'None has the right to be worshipped,' shall enter Paradise.' He said, 'Whoever says, 'None has the right to be worshipped save Allah,' and fulfils its obligations and meets its requirements, shall enter Paradise.'
Wahb ibn Munabbih was asked, 'Is not the testification that 'none has the right to be worshipped save Allah' the key to Paradise?' He replied, 'Of course, but every key has its teeth; if you bring a key that has teeth, the door shall open; but if not, it will not.'
The Key to Paradise is the testification of Tawhid. This book highlights the importance of correct belief, a true love for Allah and the state of the heart. Chapters Include: The Manner of Entering Paradise The Meaning of the Testification Loving Allah The Sound Heart
Also included is an extremely beneficial appendix - The Types of Hearts by al-Hafidh Ibn Qayyim al-Jawziyyah.